Fluid oscillator

ABSTRACT

A fluid oscillator comprised of a first conduit which emits a power jet of fluid and a second conduit which both receives the emitted jet and intermittently deflects the emitted jet with fluid pulses to sustain continuous pressure fluctuations within the second conduit. The oscillator can be used as a temperature sensor since the pulse rate of the pressure fluctuations in the second conduit is a measure of the temperature of the fluid transmitted therethrough, other factors being held constant.

United States Patent Hunter 51 Mar. 7, 1972 541 FLIUH) OSCILLATOR [72] Inventor: John M. Hunter, Granby, Conn.

[73] Assignee: Chandler Evans Inc., West Hartford,

Conn.

[22] Filed: Dec. 29, 1969 211 App1.No.: 888,456

[52] US. Cl ..l37/8l.5 [51] Int. Cl. .FlSc l/04, FlSc 3/00 [58] Field ofSearch.... ..137/81.5

[56] References Cited UNITED STATES PATENTS 3,075,548 1/1963 Horton ..137/81.5 X 3,158,166 11/1964 Warren.. ..137/815 3,234,955 2/1966 Auger.... ..137/81 5 3,258,685 6/1966 Horton ...l37/81.5 X 3,273,377 9/1966 Testerman et a1. ..137/8l.5 X

3,438,384 4/1969 Hurvitz 137/81 .5

3,448,752 6/1969 ONeill ..137/81.5 3,456,668 7/1969 Wheeler, Jr. .....137/81.5 3,491,797 1/1970 Taplin et al ..l37/81.5 3,513,868 5/1970 Halbach et al" .....137/81.5 3,529,612 9/1970 Rausch ..137/81.5

Primary Examiner-Samuel Scott Attorney-Fishman and Van Kirk [5 7] ABSTRACT A fluid oscillator comprised of a first conduit which emits a power jet of fluid and a second conduit which both receives the emitted jet and intermittently deflects the emitted jet with fluid pulses to sustain continuous pressure fluctuations within the second conduit. The oscillator can be used as a temperature sensor since the pulse rate of the pressure fluctuations in the second conduit is a measure of the temperature of the fluid transmitted therethrough, other factors being held constant.

8 Claims, 4 Drawing Figures PAIENTEDMAR 71972 sum 1 0r 2 FIG.3

FIG.2

INVENTOR JOH/VM-HUNTER ATTORNEY SHEET 2 0F 2 FLUID OSCILLATOR BACKGROUND OF THE INVENTION cally, the present invention is directed to fluid oscillators which are free-running oscillators requiring only the continuous supply of fluid. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.

2. Description of the Prior Art Fluid oscillators which continuously produce pressure pulses, free-running vibrators, are already known as described in US Pat. No. 3,244,189. Such oscillators are composed of a power jet stream which is alternately cycled between two different output branches of a flow splitter by means of control jets. The control jets may be driven from the output branches of the oscillator by means of feedback channels which transmit a portion of the output pulses alternately to the two control jets disposed at opposite sides of the power jet. Selfsustaining oscillations at the output branches result in a continuous pulse train.

The prior art devices are expensive because of the complex relationships between the power jets, the flow splitter and the positioning of the control jets and splitter from the source of the power jet. Since the splitter forms two output channels, perfect balance of the system is obtained only by perfect symmetry of the structure. Even this balance is readily destroyed because it is an unstable situation, i.e., the smallest disturbance completely upsets the balanced condition. Accordingly, it is an object of the present invention to provide fluid oscillator which is simple in construction and inexpensive to manufacture.

It is a further object of the invention to provide a simple oscillator which may produce well-defined sinusoidal outputs free of distortion.

It is still a further object of this invention to provide a fluid oscillator which can be-used as a temperature-sensing device or fluid phase discriminator.

SUMMARY OF THE INVENTION This invention relates to a fluid oscillator which produces a continuous train of fluid pulses.

The fluid oscillator of the present invention consists of a power conduit which emits a power jet and a receiving conduit to which the power jet is transmitted intermittently. The receiving conduit has a fluid entrance spaced axially from the power conduit in substantial alignment with the axis of the power jet emitted from the power conduit. The receiving conduit has a fluid exit which is disposed at an angle to the power jet emitted from the power conduit and periodically discharges a fluid pulse into the power jet to deflect the flow from the power conduit and thereby interrupt the flow at the entrance of the receiving conduit. The interruptions of the power jet create pressure perturbations in the receiving conduit as the power jet periodically impinges on the entrance to the receiving conduit. The pressure perturbations in the receiving conduit in turn produce the fluid pulses which interrupt the power jet. The operation, therefore, is made selfsustaining simply by applying a pressurized fluid continuously to the power conduit.

Sinusoidal signals can be derived from the oscillator by connecting a pressure transducer into the receiving conduit. Alternately, oscillatory signals can be derived by a pickup disposed near the entrance to the receiving conduit or in the pulsating fluid stream emitted from the receiving conduit. Further, the pressure forces of the fluid on the receiving conduit itself may be measured.

The oscillator can be employed as a temperature sensor by locating the receiving conduit in the environment to be measured or by passing a fluid whose temperature is to be measured through the oscillator. In either case, the frequency of the output pulses is temperature dependent, other factors such as the geometry of the receiving conduit and supply pressure of the fluid being held constant.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows one embodiment of the fluid oscillator constructed from tubing and a mounting block.

FIG. 2. shows a more conventional construction of the fluid oscillator formed by machined channels and chambers within a block element.

FIG. 3 is a graph showing the variation of oscillator frequency with temperature for an embodiment of the oscillator such as shown in FIG. 1.

FIG. 4 is a further embodiment of the present invention; FIG. 4 comprising a modification of the device shown in FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now to FIG. I, a first embodiment of the fluid oscillator of the present invention is disclosed. The oscillator of FIG. 1 is composed of standard parts which may be readily acquired and assembled without special casting or cutting equipment.

The oscillator, generally designated by the numeral 10, is composed of an inlet or power tube 12, a receiving tube 14 and a common supporting block 16. The power tube 12 is mounted in a drilled channel 18 on one comer of the block 16 and may be secured in place by any suitable technique such as, for'example, a press fit or soldering. Fluid is introduced into the power tube at the end 20 and is emitted in a power jet at an exit end 22. The power jet issues towards the entrance 24 of the receiving tube 14.

The entrance end of the receiving tube 14 is mounted in a projection of the block 16 in a manner similar to the inlet tube 12. The tube 14 is secured within a drilled channel 26 which is preferably coaxial with the channel 18. During the manufacture of the block 16, channels 18 and 26 may be drilled at the same time by advancing the cutting drill directly from one side of the block 16 to the other in a single pass.

In the embodiment of FIG. 1, the receiving tube 14 is bent in a smooth 270 curve so that the pulsing exit 28 can be secured in a drilled channel 30 at a position substantially to the axis of channels Band 26. Again the tube 12 can be secured within the channel 30 by a press fit or soldering. The exit end 28 is disposed adjacent to the exit 22 of tube 12, at a station within the axial spacing between the jet exit 22 and the receiving entrance 24, and in a plane transverse to the power stream axis.

If desired a mounting hole 32 can be drilled on a boss 34 on one corner of the block 16.

Operation of the oscillator is achieved by connecting the power tube 12 to a source of fluid under pressure. This may be accomplished by simply sliding a tight-fitting hose from the source over the tube 12 at the entrance end 20. As the initial quantity of fluid passes through the power tube 12 it is emitted as a free jet from exit 22, spans the open space cutout 36 in block 16 and impinges on the entrance 24 of receiving tube 14. At least a quantity of the power jet passes into tube 14 and a similar quantity of fluid is expelled in a pulsed fluid jet at the exit 28. Since the axis of channel 30 intersects the axes of channels 18 and.26 at an angle, and preferably at an angle of 90, the jet leaving exit 28 interrupts the power jet and momentarily deflects the jet away from the entrance 24. The interruption of the power jet impacting on the entrance 24 drops the pressure at the entrance 24 suddenly and, according to one theory, produces a pressure expansion wave which travels through the tube 14. As the pressure wave reaches the exit 28, the pulse of fluid which deflects the power jet is momentarily depleted and the power jet again impacts on the entrance 24 of tube 14. When the power jet reestablishes contact with the entrance 24, a compression wave is transmitted through the tube 14 and reestablishes a fluid pulse at the exit 28 to again interrupt the impacting of the power jet on entrance 24.

Through the repeated interactions of the power jet and interrupting jet, a continuous train of alternating expansion and compression waves are transmitted through the receiving tube 14. The frequency with which these waves traverse the length of tube 14 characterizes the operating frequency of the fluid oscillator.

Since the frequency of the oscillator is determined by the alternating expansion waves and compression waves within tube 14, the frequency can be varied by a number of parameters which affect the travel time of the waves within the tube 14. The travel time in tube 14 depends upon the speed of the wave and the length of the tube 14. Speed, in turn, varies according to the temperature of the fluid, the characteristics of the fluid itself such as its compressibility and density and the characteristics of the receiving tube itself. The oscillator of the present invention can, of course, be used with either liquids or gases.

If a gas is used to' operate the oscillator, the inlet pressure of the gas changes the frequency, f, of the oscillator as indicated in FIG. 3. In one embodiment of the oscillator, the curves represented by P,, P and P were made with nitrogen gas at pressures of p.s.i.g., p.s.i.g. and 40 p.s.i.g. respectively. FIG. 3 also represents the variation of frequency, f, with temperature, T. The arrows adjacent the axes of the graph indicate increasing frequency and increasing temperature. At the gas pressure of 10 p.s.i.g. the frequency versus temperature gradient at room temperature is approximately 20 c.p.s. per 100 F. where the temperature plotted is that of the gas admitted to tube 12. The temperature dependency teaches that the oscillator can be.used as a temperature sensor with other factors such as the gas pressure and geometry of tube 14 being known.

The oscillator may be used in several ways to measure tern: perature. If the temperature of the gas itself is to be measured, it is simply necessary to leak a small quantity of the gas through the oscillator. The temperature is measured by detecting the oscillator frequency and comparing the detected frequency with the characteristic frequency-temperature curves as shown in FIG. 3. If the temperature of an environment other than the gas driving the oscillator is to be measured, the power tube 12 or the receiving tube 14 may be disposed within the environment to heat or cool the gas operating the oscillator. Again the detected frequency would be related to the temperature by the characteristic curves. Because there are relatively high fluid flow rates through the oscillator, the length of the tubes 12 and 14 may be lengthened to increase the surface area for heating the fluid and thereby increase the sensitivity of the oscillator to temperatures of environments other than the operating fluid itself. Preheating or precooling the fluid to establish a large temperature differential between the fluid and the environment will also aid the temperature sensitivity of the oscillator.

In order to develop the output of the oscillator when the operating fluid is a gas, a pressure wave sensor such as a microphone 40 may be located in the vicinity of entrance 24. The sweeping of the power jet back and forth across the edges of the tube 14 at the entrance 24 produce edge tones which are readily detected by the microphone 40 and transformed into electrical signals for use as desired. If the fluid oscillator is to be used as a temperature sensor, the electrical signals from the microphone would be supplied to a discriminator and developed into a voltage which could be applied to a meter calibrated directly in degrees of temperature.

The oscillator 10 may also be used as a fluid phase discriminator. Since the frequency at which the oscillator operates is dependent upon the type of fluid being supplied to the oscillator, a change in the fluid will produce a change in the operating frequency. When the fluid phase changes between that of a liquid and a gas there will be a significant change in the frequency of the oscillator.

As shown in H6. 4, one embodiment of the oscillator which is particularly suited to detecting the frequency change when the oscillator is used as a phase discriminator includes one or two flexible tube sections, such as section 14A, in the tube l4 intermediate one or both of the connections with block 16. In such case the intermediate section 14A of the tube is free to deflect under the influence of the fluid pressure pulses transmitted through the tube 14. These fluid pulses are substantially stronger for a liquid phase than for a gaseous phase and have different frequency characteristics as mentioned above. By attaching a strain gauge 41 or a position transducer to the flexible, intermediate portion 14A of tube 14, the change in either the amplitude of the tube vibrations or the frequency of the tube vibrations can be detected when the phase of the fluid in tube 14 changes between the liquid and gaseous states.

Such a detector may be desirable in missile fuel systems where it becomes important to either control or recognize the change in the state of a fuel or an oxidizer.

Reference to FIG. 2 discloses an alternate embodiment of my oscillator constructed in accordance with more conventional practices in the fluidics art.

In FIG. 2 the oscillator, here generally designated 50, is formed principally by machining channels and chambers within a block 52. An inlet power channel 54 introduces pressurized fluid into the interrupting chamber 56 which is hogged out within a central region of the block 52. Disposed substantially in alignment with the exit 58 of inlet channel 54 and at the opposite side of chamber 56 is an entrance 60 to a receiving channel 62. The channel 62 terminates at a pulsing exit 64 transversely of the power jet exit 58. A discharge channel 66 leads from the chamber 56 at a position opposite the exit 64 to the exterior of block 52. Fluid scavenging ports 68 and 70 are located at the receiving end of the chamber 56 and are connected to a vent port (not shown).

The operation of the oscillator 50 differs little in substance from the operation of the oscillator 10 in FIG. 1. Pressurized fluid is introduced into channel 54 and establishes a power jet within chamber 56. The power jet is periodically deflected from the entrance 60 of receiving channel 62 by the interrupting jet emitted at exit 64 of the channel 62. The interrupting jet is directed toward channel 66 which may be connected to a low-pressure environment to induce a strong directional tendency of the interrupting jet and thereby insure deflection of the power jet from the entrance 60. The fluid of the deflected power jet is readily absorbed through the large scavenging ports 68 and 70. As in the oscillator 10, the impact of the power jet on the entrance 60 establishes a train of expansion and compression waves in the channel 62 which form the selfsustaining pulses of the interrupting jet at exit 64.

An alternate pressure wave sensor 72 is shown connected to the receiving channel 62 by means of a passageway 74. The sensor 72 is a high-response pressure transducer detecting the pressure waves traveling in channel 62. Where a gas is used to operate the oscillator, the pressure transducer 72 provides exceptionally clean sinusoidal signals through the leads 76. The detection of the waves by the pressure transducer can be further improved by tuning the channel 74 for resonance with the wavelength of the pressure waves in the tube 14. If the length of passageway 74 is selected to set up resonant standing waves with the pressure waves in tube 14, strong and clean sinusoidal waves will be detected by the transducer 72.

The oscillator 50 in FIG. 2 may also be used as a temperature-sensing device by operating the oscillator with a gas at the temperature which is to be measured.

The shape of the output signal of the fluid oscillators 10 and 50 can be varied by changing the geometry of the device. For example, the exit 22 and the entrance 24 may be moved closer to one another and the exit 28 may be shifted between the exit 22 and the entrance 24 to develop different deflection characteristics at the entrance 24. Also, a slight misalignment of the entrance 24 and the exit 22 produces a pulselike waveform.

While several embodiments of the fluid oscillator are dis closed, it will be understood that various modifications can be made to the oscillators without changing the principal mode of operation. For example, the shape of the receiving tube 14 may be changed from a smooth bending circular form to an lOl026 (H87 angled rectangular form. The tube 14 may also be lengthened to change the frequency characteristics of the oscillator by a series of bends in a tortuous configuration or a spiral. In addition, the pressure transducer 72 may be substituted as the pressure wave sensor in FIG. 1 by connecting the transducer with tube 14. The pressure wave sensor in such case has a direct communication similar to that shown in FIG. 2 with the tube 14 rather than the indirect communication provided through the edge tones from entrance 24.

What is claimed is: 1. A fluid oscillator comprising: first fluid conduit means having an exit for emitting a fluid power jet along a jet axis; 7 second fluid conduit means defining a closed fluid circuit having a first end spaced axially along the jet axis and substantially aligned with the axis to receive at least a portion of the power jet emitted by the first fluid conduit means and a second end of the second fluid conduit means disposed laterally of the jet axis, at an angle to the jet axis and at a position intermediate the exit of the first fluid conduit means and the first end of the second fluid conduit means for producing deflecting fluid pulses in the powerjet stream; and a sound-responsive transducer positioned adjacent to the first end of the second fluid conduit means for generating an output signal commensurate with the frequency of oscillation of said fluid oscillator. 2. The fluid oscillator of claim 1 wherein: the first fluid conduit means and the second fluid conduit means are tubes mounted within a common supporting structure. 3. The fluid oscillator of claim 1 wherein: the first fluid conduit means and the second fluid conduit means are fluid channels defined within a block structure. 4. The fluid oscillator of claim 1 wherein: the second fluid conduit means comprises a length of tubmg. 5. The fluid oscillator of claim 4 wherein: the length of tubing defines a smooth bending curve at an intermediate portion of the tubing. 6. A fluid oscillator comprising:

first fluid conduit means having an exit for emitting a fluid power jet along a jet axis; second fluid conduit means defining a closed fluid circuit having a first end spaced axially along the jet axis and substantially aligned with the axis to receive at least a portion of the power jet emitted by the first fluid conduit means and a second end of the second fluid conduit means disposed laterally of the jet axis, at an angle to the jet axis and at a position intermediate the exit of the first fluid conduit means and the first end of the second fluid conduit means for producing deflecting fluid pulses in the power jet stream; and a pressure-responsive transducer connected to the second fluid conduit means intermediate the first and second ends thereof for generating signals commensurate with the frequency of said oscillator. 7. The fluid oscillator of claim 6 wherein: third fluid conduit means interconnects the transducer with the second fluid conduit means, the length of the third fluid conduit means being a resonant length to establish standing waves in tune with the pressure fluctuations in the second conduit means. 8. A fluid oscillator comprising: first fluid conduit means having an exit for emitting a fluid power jet along a jet axis; second fluid conduit means defining a closed fluid circuit having a first end spaced axially along the jet axis and substantially aligned with the axis to receive at least a portion of the power jet emitted by the first fluid conduit means, the second end of said second fluid conduit means being disposed laterally of the jet axis at a position intermediate the exit of the first fluid conduit means and the first end of the second fluid conduit means and oriented at an angle to the jet axis for producing deflecting fluid pulses in the power jet stream, said second fluid conduit means including a tubular member flexibly connected in said second conduit means intermediate the first and second ends thereof; and

a deflection transducer connected to said tubular member for detecting tube deflections. 

1. A fluid oscillator comprising: first fluid conduit means having an exit for emitting a fluid power jet along a jet axis; second fluid conduit means defining a closed fluid circuit having a first end spaced axially along the jet axis and substantially aligned with the axis to receive at least a portion of the power jet emitted by the first fluid conduit means and a second end of the second fluid conduit means disposed laterally of the jet axis, at an angle to the jet axis and at a position intermediate the exit of the first fluid conduit means and the first end of the second fluid conduit means for producing deflecting fluid pulses in the power jet stream; and a sound-responsive transducer positioned adjacent to the first end of the second fluid conduit means for generating an output signal commensurate with the frequency of oscillation of said fluid oscillator.
 2. The fluid oscillator of claim 1 wherein: the first fluid conduit means and the second fluid conduit means are tubes mounted within a common supporting structure.
 3. The fluid oscillator of claim 1 wherein: the first fluid conduit means and the second fluid conduit means are fluid channels defined within a block structure.
 4. The fluid oscillator of claim 1 wherein: the second fluid conduit means comprises a length of tubing.
 5. The fluid oscillator of claim 4 wherein: the length of tubing defines a smooth bending curve at an intermediate portion of the tubing.
 6. A fluid oscillator comprising: first fluid conduit means having an exit for emitting a fluid power jet along a jet axis; second fluid conduit means defining a closed fluid circuit having a first end spaced axially along the jet axis and substantially aligned with the axis to receive at least a portion of the power jet emitted by the first fluid conduit means and a second end of the second fluid conduit means disposed laterally of the jet axis, at an angle to the jet axis and at a position intermediate the exit of the first fluid conduit means and the first end of the second fluid conduit means for producing deflecting fluid pulses in the power jet stream; and a pressure-responsive transducer connected to the second fluid conduit means intermediate the first and second ends thereof for generating signals commensurate with the frequency of said oscillator.
 7. The fluid oscillator of claim 6 wherein: third fluid conduit means interconnects the transducer with the second fluid conduit means, the length of the third fluid conduit means being a resonant length to establish standing waves in tune with the pressure fluctuations in the second conduit means.
 8. A fluid oscillator comprising: first fluid conduit means having an exit for emitting a fluid power jet along a jet axis; second fluid conduit means defining a closed fluid circuit having a first end spaced axially along the jet axis and substantially aligned with the axis to receive at least a portion of the power jet emitted by the first fluid conduit means, the second end of said second fluid conduit means being disposed laterally of the jet axis at a position intermediate the exit of the first fluid conduit means and the first end of the second fluid conduit means and oriented at an angle to the jet axis for producing deflecting fluid pulses in the power jet stream, said second fluid conduit means including a tubular member flexibly connected in said second conduit means intermediate the first and second ends thereof; and a deflection transducer connected to said tubular member for detecting tube deflections. 